Field
Apparatuses and methods consistent with the exemplary embodiments relate to a power supply, a power control method thereof and a display apparatus having the same, and more particularly to a power supply, a power control method thereof and a display apparatus having the same, in which analog dimming and pulse width modulation (PWM) dimming for adjusting optical power of a light source such as a backlight unit of a display are performed by one circuit.
Description of the Related Art
In general, a display apparatus such as a television (TV) includes a power supply. For example, a switching mode power supply (SMPS) may be used to supply operation power to a power supplying target such as a display, etc. The power supply receives commercial alternating current (AC) power and converts the commercial AC power into operation power having a level needed for the power supplying target, thereby supplying the operation power to the power supplying target.
If the power supplying target is a light source, for example, a light emitting diode (LED) bar of the backlight unit, the power supply has to control optical output of the LED bar based on an image displayed on the display. To this end, the power supply typically uses one of the analog dimming and the PWM dimming to adjust the optical output of the LED bar.
However, both dimming methods have some problems. Specifically, the analog dimming adjusts average current intensity of the LED bar, and therefore may cause change in LED color as the LED bar is driven by different currents. The PWM dimming changes a duty cycle to which the maximum current for operating the LED bar is applied, and thus rapidly repeats an operation of turning on and off the LED bar for a short period of time. Therefore, the PWM dimming has to keep turning on and off the LED bar at a frequency higher than a certain bandwidth, e.g., about 200 Hz, so that a viewer cannot feel any flicker.
To resolve these problems, a hybrid dimming method was proposed recently, which enables the power supply to selectively perform one of the analog dimming and the PWM dimming as necessary.
However, the hybrid dimming method also has problems that circuit configurations are complicated and its design and maintenance are difficult. This is because the power supply needs both a circuit for the analog dimming and a circuit for the PWM dimming. Further, a response characteristic is deteriorated when the analog dimming is switched to the PWM dimming.